Selfwinding

Selfwinding, or automatic winding, refers to mechanisms that wind a power source using the device’s own motion or energy rather than requiring manual input. The term is most commonly applied to mechanical watches, where the goal is to keep the mainspring wound with everyday wear.

In an automatic wristwatch, a weighted rotor pivots freely on a bearing and moves with wrist motion. The rotor’s rotation engages a gear train that winds the mainspring, storing energy to power the watch. Many designs use bidirectional winding and a slipping clutch to prevent overwinding and wear. The amount of winding depends on the wearer’s activity, the rotor design, and the mainspring’s condition. When not worn, some watches continue to run for a period determined by their power reserve, typically ranging from about 40 to 80 hours or more.

History and development: The concept traces back to the 18th century with inventors such as Abraham-Louis Perrelet, who experimented with self-winding mechanisms. The first practical self-winding wristwatch is generally attributed to John Harwood in the 1920s, and automatic winding became widely adopted by Swiss and other watchmakers thereafter. Over time, refinements have focused on reducing friction, improving winding efficiency, and extending power reserve, while maintaining reliability and durability.

Other uses: While the term selfwinding is most often associated with watches, similar self-winding principles appear in various mechanical systems that harvest motion to maintain energy or tension. In horology, selfwinding remains a standard feature for many mechanical watches, though some models retain manual winding as a fallback or to reset the mainspring after long periods of inactivity.